Multiple OUTPUT clauses in MERGE/INSERT/DELETE SQL commands?

Question

I have a T-SQL script that implements some synchronization logic using OUTPUT clause in MERGEs and INSERTs.

Now I

Answer 1

The OUTPUT clause allows for a selectable list. While this doesn't allow for multiple result sets, it does allow for one result set addressing all actions.

::=
{
    [ OUTPUT  INTO { @table_variable | output_table }
        [ (column_list) ] ]
    [ OUTPUT  ]
}

I overlooked this myself until just the other day, when I needed to know the action taken for the row didn't want to have complicated logic downstream. The means you have a lot more freedom here. I did something similar to the following which allowed me to use the output in a simple means:

DECLARE @MergeResults TABLE (
    MergeAction VARCHAR(50),
    rowId INT NOT NULL,
    col1 INT NULL,
    col2 VARCHAR(255) NULL
    )

MERGE INTO TARGET_TABLE AS t
    USING SOURCE_TABLE AS s
    ON t.col1 = s.col1
WHEN MATCHED
    THEN
        UPDATE
        SET [col2] = s.[col2]
WHEN NOT MATCHED BY TARGET
    THEN
        INSERT (
            [col1]
            ,[col2]
            )
        VALUES (
            [col1]
            ,[col2]
            )
WHEN NOT MATCHED BY SOURCE
    THEN
        DELETE
OUTPUT $action as MergeAction, 
    CASE $action 
        WHEN 'DELETE' THEN deleted.rowId 
        ELSE inserted.rowId END AS rowId,
    CASE $action 
        WHEN 'DELETE' THEN deleted.col1 
        ELSE inserted.col1 END AS col1,
    CASE $action 
        WHEN 'DELETE' THEN deleted.col2 
        ELSE inserted.col2 END AS col2
    INTO @MergeResults;

You'll end up with a result set like:

| MergeAction | rowId | col1 | col2 |
| INSERT      | 3     | 1    | new  |
| UPDATE      | 1     | 2    | foo  |
| DELETE      | 2     | 3    | bar  |